Differential Scanning Calorimetry has been used to investigate the mechanism
of the isothermal crystallization kinetics in Fe80B20 Metallic glass. It is shown that the whole crystallization
analysis must include, not only a crystal nucleation-and-growth process, but
also a grain-growth process and that these two processes are separated in
time during isothermal annealing. These processes have been studied directly
finding the parameters which characterize their Mechanism. From the
theoretical Johnson-Mehl-Avrami equation describing the
nucleation-and-growth process, it was possible to calculate the evolution of
the transformed fraction of the material as a function of the annealing
time. To infer the meaning of the transformed fraction, samples subjected to
different thermal treatments have been studied by Mössbauer Spectroscopy.
Our results reveal that the transformed fraction is the sum of the
crystalline component formed by all atoms located in the lattice of the
grains and the interfacial component composed of atoms in the interfacial
regions between grains.